java图形化界面实现登录窗口

//模拟qq登录窗口import java.awt.*;import java.io.*;import java.awt.event.*;import javax.swing.*;public class QQGUI extends JFrame implements ActionListener{ private JLabel userLa; private JLabel pwdLa; private JLabel verCodeLa;//验证码 private JTextField userTxt; private JPasswordField pwdTxt; private JTextField verCodeTxt;//验证码 private JButton sureBt; private JButton quitBt; private Mypanel mp; //构造方法 public QQGUI() {  Init(); } public void Init() {  Frame frame = new Frame("QQ登录");  //创建出控件对象（因为上面只是声明出来，并没有给出实际的空间)  //用户文本  userLa = new JLabel();  userLa.setText("用户名：");  userLa.setSize(60, 50);  userLa.setLocation(100, 80);  //密码文本  pwdLa = new JLabel();  pwdLa.setText("密码：");  pwdLa.setSize(50, 50);  pwdLa.setLocation(100, 120);  //用户输入框  userTxt = new JTextField();  userTxt.setSize(100, 20);  //this.setSize(width, height)  userTxt.setLocation(170, 95);  //密码输入框  pwdTxt = new JPasswordField();  pwdTxt.setSize(100, 20);  pwdTxt.setLocation(170, 135);  //确认按钮  sureBt = new JButton("登录");  sureBt.setSize(60, 25);  sureBt.setLocation(135, 260);  //退出按钮  quitBt = new JButton("退出");  quitBt.setSize(60, 25);  quitBt.setLocation(240, 260);  //验证码文本  verCodeLa = new JLabel();  verCodeLa.setText("验证码：");  verCodeLa.setSize(60, 50);  verCodeLa.setLocation(100,165);  //验证码文本框  verCodeTxt = new JTextField();  verCodeTxt.setSize(100, 20);  verCodeTxt.setLocation(170, 180);  //验证码  mp = new Mypanel();  mp.setSize(100, 30);  mp.setLocation(280, 175);  //登录方式选择框  JComboBox xlk=new JComboBox();  xlk.setSize(60, 20);  xlk.setLocation(250, 220);  xlk.addItem("在线");  xlk.addItem("隐身");  xlk.addItem("离开");  this.setLayout(null);  this.setSize(500, 400);  this.add(userLa);  this.add(pwdLa);  this.add(userTxt);  this.add(pwdTxt);  this.add(sureBt);  this.add(quitBt);  this.add(verCodeLa);  this.add(verCodeTxt);  this.add(mp);  this.add(xlk);  sureBt.addActionListener(this);  quitBt.addActionListener(this);  this.setVisible(true); } //具体事件的处理  public void actionPerformed(ActionEvent e)  {   //获取产生事件的事件源强制转换   JButton bt = (JButton)e.getSource();   //获取按钮上显示的文本   String str = bt.getText();   if(str.equals("登录"))   {    if(!CheckIsNull())    {     //获取用户所输入的用户名     String user = userTxt.getText().trim();     //获取用户所输入的密码     String pwd = pwdTxt.getText().trim();     if(checkUserAndPwd(user,pwd))     {      //隐藏当前登录窗口      this.setVisible(false);      //验证成功创建一个主窗口      MainFrame frame = new MainFrame();     }     else     {      //如果错误则弹出一个显示框      JOptionPane pane = new JOptionPane("用户或密码错误");      JDialog dialog = pane.createDialog(this,"警告");      dialog.show();     }    }   }   else   {    //调用系统类中的一个正常退出    System.exit(0);   }  }  private boolean CheckIsNull()  {   boolean flag = false;   if(userTxt.getText().trim().equals(" "))   {    flag = true;   }   else   {    if(pwdTxt.getText().trim().equals(" "))    {     flag = true;    }   }   return flag;  }  private boolean checkUserAndPwd(String user,String pwd)  {   boolean result = false;   try   {    FileReader file = new FileReader("D://Workspaces//MyEclipse 8.5//testGUI.txt");     BufferedReader bre = new BufferedReader(file);    String str = bre.readLine();   while(str!=null)   {     String[] strs = str.split(",");     if(strs[0].equals(user))     {      if(strs[1].equals(pwd))      result = true;     }     str = bre.readLine();   }   file.close();   }catch(Exception ex)   {    System.out.print("");   }   return result;  }}//MainFrame类import javax.swing.*;public class MainFrame extends JFrame { public MainFrame() {  this.setSize(300, 300);  this.setVisible(true); }}//验证码的生成import java.awt.*;import java.util.*;public class Mypanel extends Panel { public void paint(Graphics g) {  int height = 50;  int width = 90;  //验证码框背景颜色  g.setColor(Color.LIGHT_GRAY);  //填充验证码背景  g.fillRect(0, 0, width, height);  g.setColor(Color.BLACK);  g.drawRect(0, 0, width-1, height-1);  Random r = new Random();  //设置干扰点  for(int i = 0;i<100;i++)  {   int x = r.nextInt(width)-1;   int y = r.nextInt(height)-1;   g.drawOval(x, y, 2, 2);  }  g.setFont(new Font("黑体",Font.BOLD,20));//设置验证码字体以及大小  g.setColor(Color.RED);//设置验证码字体颜色  //生成随机验证码  char[] tmp = ("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ").toCharArray();  StringBuilder sb = new StringBuilder();  for(int i = 0;i<4;i++)  {   int pos = r.nextInt(tmp.length);   char c = tmp[pos];   sb.append(c + " ");  }  g.drawString(sb.toString(), 10, 15);//写入验证码 }}//下拉框的实现import java.awt.*;import java.awt.event.*;import javax.swing.*;public class xialakuang extends JFrame { private JComboBox comboBox;//定义一个组合框 public void xia () {  //JPanel panel = new JPanel();//创建一个JPanel面板  comboBox = new JComboBox();  comboBox.addItem("在线");  comboBox.addItem("隐身");  comboBox.addItem("离开");  this.add(comboBox);  //this.add(panel);  this.setSize(200, 100);  this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);  this.setVisible(true); }}//测试public class testQQGUI { /**  * @param args  */ public static void main(String[] args) {  // TODO Auto-generated method stub  QQGUI frame = new QQGUI(); }}